Among radio communication technologies, a new system has been defined in order to use a wider frequency band and an increased number of information bits per band and thus, achieve improved throughput. In some technologies, when a new system is introduced, throughput is improved through cooperation (concurrent communication) with an existing system (see, e.g., Japanese Laid-Open Patent Publication No. H6-045991). Technologies of cooperation between a new system and an existing system include cooperation among multiple systems and cooperation among multiple bands.
For example, a base station collects communication states of mobile stations, determines whether to perform cooperation between a new system and an existing system based on the collected communication states, and notifies the mobile stations and nearby base stations of a decision to control the concurrent communication.
However, in the conventional technique described above, in order for the base station to determine whether to perform concurrent communication, the communication state of a mobile station is reported to the base station by the mobile station, putting pressure on control channel radio resources and reducing data communication throughput. If the mobile station less frequently notifies the base station of the communication state, triggering of the concurrent communication is delayed, making effective concurrent communication impossible.
For example, when delay tolerance of a Voice over IP (VoIP) bearer is 100 [ms] and a period of notification of a communication state from a mobile station to a base station is several hundred [ms], a loss of several packets occurs due to a delay of the triggering of the concurrent communication, leading to characteristic deterioration.